Plants are distributed in different habits of aquatic, moderate and severally dry terrestrial nature, thus termed as hydrophytes, neophytes and xerophytes, respectively.
Hydrophytes have the adaptations to remove the flooding of its cells in fresh water. In this type surface area of leaves is very large to transpire water excessively. Extensive stomata are present on the upper surface area facing the atmosphere to promote loss of water.
Mesophytes have moderate water availability. In sufficient supply of water stomata are kept open to promote loss of excess water, however, in restricted supply stomata Close to prevent the loss e.g. Brassica, rose, mango etc.
Xerophytes have adaptations for reduced rate of transpiration. Many xerophytes possess small, thick leaves to limit water loss by reducing surface area proportional to the volume. Their cuticle is thick, waxy and leathery. Stomata are on lower surface of leaves and located in depression. Some as cacti, during the driest season, shed their leaves to restrict transpiration completely, thus stems are the photosynthetic organs. In rainy season, stem stores water for use in dry conditions.
Osmoregulation in Animals
Animal cells require more critical balance of water and solutes in the body as they cannot survive a net water gain or loss. Water continuously leaves and enters the cells; however, the quantity of the water and the solutes is kept in balanced. There are two approaches in maintaining this balance.
Animal body fluids are kept isotonic to the external environment even for marine saltwater environment. These animals thus do not require actively to adjust their internal osmotic state so are known as Osmoconformers. Animal body fluids are kept isotonic to the external environment even for marine saltwater environment. These animals thus do not require actively to adjust their internal osmotic state so are known as Osmoconformers.
The animals whose body fluid concentrations differ noticeably the outside environment actively regulate to discharge excess water in hypotonic and excrete salts in hypertonic conditions therefore, are called as Osmoregulators. Animals inhabiting different environments have distinct adaptations to regulate osmotic balance, e.g. marine fresh water and terrestrial environments.
Osmoregulation in Different Environments
Most marine invertebrates are Osmoconformers. Among the vertebrates hagfishes are isotonic with the surrounding sea’s water. Most cartilaginous fishes maintain lower internal salt concentration than that of sea’s water .They kidneys for osmoregulation excrete salts through gills and also possess salt excreting organs such as rectal glands. These employ active transport mechanism to remove salt against osmotic gradient. Some fishes have relatively low salt in body fluids but have rendered these hypertonic to that of sea’s water by retaining urea in adequate concentration. Because urea in high concentration is damaging so these fishes retain another chemical trimethylamine oxide for protection against urea Bony fishes, the descendants of fresh water ancestors but later became marine constantly lose water from their hypotonic body fluids to hypertonic environments. These fishes have adapted themselves to drink large amount of seas water and excrete concentrated urine resulting in maximum salt excretion and minimum water loss.
2. Fresh Water
Fresh water animals are constantly facing the osmotic flooding of body fluids and loss of salts. Fresh water protozoa, Amoeba and Paramecium pump out excess water by structures contractile vacuoles. Many fresh water animals including fishes remove excess water by producing large volumes of very dilute urine. The loss of salts is compensated by preference of salt containing food and by active uptake of salts by gills and skin.
The evaporative loss of water leading to dehydration is the major problem for terrestrial life. Arthropods and vertebrates have successfully adapted to terrestrial mode of life. Terrestrial animals are covered by body surface, which prevents loss of water as the waxy exoskeletons of insects and multi-layered dead, skin cells most terrestrial vertebrates. Drinking and eating moist foods compensate the loss of water. There animals also have metabolic and behavioral adaptations. Some desert plants containing more carbohydrates, which produce water of metabolism. Terrestrial animals produce concentrate urine in their kidneys that reabsorb most filtered water in the process of excretion. Terrestrial animals can tolerate dehydration and it differs in various animals. This characteristic is known as .
Guy’s thanks for visiting my article hope you get Knowledge from it.